1. Field of the Invention
The present invention relates to a backflow preventer and, more particularly, to a modular fluid arrangement for a check valve to prevent backflow through the check valve.
2. Description of Related Art
Fluid valves generally include a main body having two ends. The main body also forms an internal flow cavity that fluidly connects the two ends and houses internal valves. In a typical installation, one end of the main body is connected to a fluid inlet pipe and the other end is connected to a fluid outlet pipe. Fluid flows from the fluid inlet pipe, through the internal flow cavity, is stopped, directed, or left unimpeded by the internal valves, and exits through the fluid outlet pipe. Such fluid valves can include backflow prevention valves, which ensure that fluid flow always flows in one direction. When, for various reasons, fluid does try to flow backward, the safest and most effective device for stopping the backflow is a “reduced pressure principle” backflow valve.
Some fluid backflow valves have movable parts, such as two independently acting check valves positioned in the internal flow cavity formed by a main body and, as a failsafe, a differential pressure relief valve (RV) attached to a port of the main body. The RV acts as a failsafe because, in a backflow condition, even if the check valves fail, the RV will ensure that no downstream fluid is permitted to flow into an upstream fluid supply line by dumping potential backflow fluid to the atmosphere. Generally, most RV's are controlled internally by a pressure differential acting across a diaphragm. Typically, high pressure acting on one side (i.e., high side) of a diaphragm will force a rubber seal ring to abut against a “seat” edge, thus creating a water-tight seal. When the force due to pressure acting on an opposite side (i.e., low side) of the diaphragm acting in conjunction with a spring exceeds the high side force, the seal and seat edge will separate and open up a flow path for the fluid to escape. In essence, the diaphragm acts as a switch that opens and closes the flow path of the RV. Because the RV operation depends heavily on the diaphragm, which is typically made of an elastomeric material, a larger size diaphragm is generally used to provide for a stronger, more robust and positive RV operation. However, the advantages of a larger diaphragm have to be weighed against the disadvantages associated with a larger size diaphragm, often resulting in an overall bulkier valve design.
The repair, inspection, or replacement of the fluid valves (i.e., check valves and RV) within the backflow prevention valve typically requires the flow of fluid to be shut off. An inlet shutoff valve, or some other member, as shown in U.S. Pat. Nos. 1,969,432; 3,245,257; 3,946,754; 4,327,760; 5,392,803; 5,511,574; and 5,732,744, is typically positioned adjacent one end of the main body and an outlet shutoff valve is positioned adjacent the other end of the main body. In turn, each shutoff valve is connected, respectively, to the fluid inlet pipe or the fluid outlet pipe. The shutoff valves are required for testing and service of the backflow prevention valve. Access to internal components of such fluid valves is typically accomplished through one or more access ports or openings. Under certain regulatory codes, the main body, which houses the fluid valves, cannot be completely removed from the fluid handling system during routine maintenance and inspection of the valves. In other instances when the main body is in a location that is not easily accessible to maintenance personnel, maintenance and inspection of such valves can become difficult.
In some fluid handling installations, a bypass line is often used to maintain fluid flow through the system, while selected ones of the fluid valves of the system are either being repaired, inspected, or replaced. This bypass line adds additional costs and takes up extra space in the fluid handling installation. In some installations, a minor disruption in the fluid flow may not result in serious adverse consequences downline of the fluid handling installation and a bypass line is not required. Therefore, if the time of repair, replacement, or inspection of a fluid valve can be minimized, an additional bypass line may not be required.
Therefore, it is an object of the present invention to overcome the above-mentioned deficiencies by providing a modular fluid arrangement for a check valve that provides for easy maintenance and replacement of check valves, with minimal disruption of the flow in a fluid handling installation. It is also desirable to provide a compact and space-efficient modular fluid arrangement, while providing a strong, robust, and positive RV operation.